Thermally insulating fluid

ABSTRACT

A thermally insulating fluid composition comprising a glycol solvent for a viscosifier, a viscosifier, and optionally, an aqueous brine. The glycol may be selected from a propylene glycol, or under excessive heat temperatures, a butylene glycol, which can be used with or without a viscosifier. Viscosifiers can be selected from hydroxy propyl methyl cellulose, xanthan and hydroxy propyl guar and combinations thereof. In one method of producing the thermally insulating composition, a viscosifier is added to an aqueous brine, water is then added to that solution followed by the addition of dry salt of the brine to increase density if necessary. A propylene glycol solvent is added to the resulting solution. The thermally insulating fluid composition insulates substances stored or transported in multi-walled vessels, tanks, piping and thermal units. A method of applying the insulating fluid composition of this invention comprising the steps of injecting the thermally insulating fluid into the cavity formed by two adjacent walls of the vessel or piping and then sealing off the opening.

FIELD OF THE INVENTION

[0001] The present invention relates to a composition for a thermallyinsulating fluid, the method of producing a thermally insulating fluidand a method of insulating multi-walled containers. More specificallythe invention relates to a thermal insulating fluid comprising one ormore glycols and a viscosifier.

BACKGROUND OF THE INVENTION

[0002] Low thermal conductivity is desirable in many industrial andconsumer applications for the purposes of maintaining fluids or solidswithin a specific temperature range. Thermal containers for foods,insulated tanks and piping for storage and transportation of temperaturesensitive fluids and oil field tubing require thermal insulatingqualities under varying environmental conditions. Currently, as oilfield production seeks deeper drilling, both offshore and in certainland fields, such as the atmospheric environs of Alaska, the retentionof high temperatures within the tubing is necessary to inhibit theaccumulation of asphaltene and paraffin inside pipes. The outer hull ofparticular chemical storage tanks as well must have thermal insulatingqualities, for example, gasoline storage tanks and liquid ammonia tanks.Thermal properties are necessary in the ammonia storage tanks tomaintain aqueous ammonia in its liquid state, requiring temperaturesbelow 65° F.

[0003] Various insulating compositions and methods are well known. Oneubiquitous fluid composition used asbestos as the insulating component.Asbestos is now a known human health hazard. Its choice as an insulatingcomponent is no longer viable. Naturally porous rocks such asvermiculite and perlite have been used for insulating purposes,although, their past use has been limited to solid state compositions.In the event storage vessels or piping need to be disassembled forrepair or reconditioning of the insulating material, a composition in asolid state increases down time and the repair problems because of thedifficulty of removal thereby increasing cost of production.

[0004] U.S. Pat. No. 4,276,936 given to McKinzie discloses a method ofthermally insulating the borehole of a well. McKinzie '936 teaches theuse of a solid material having thermal insulating properties, such asvermiculite and perlite. The '936 reference discloses that the solidinsulating material is introduced into the annulus in the absence of acarrier liquid and is removed by fluidization of the material.

[0005] Viscosifiers and vicosifying gels are used to fluidize solidparticulates. U.S. Pat. No. 4,530,402 given to Smith et al. disclosesthe use of a low density spacer fluid and then displacing the lowdensity fluid with a completion fluid such as cement slurry. The Smith'402 reference teaches the low density spacer fluid is comprised of acarrier fluid, which can contain a viscosifying agent, and discretedispersible density reducing bodies. The '402 reference teaches the useof dispersible reducing bodies such as hollow spheres in the spacerfluid. Smith '402 teaches that the hollow spheres aid in reducing thehydrostatic head of the spacer fluid.

[0006] U.S. Pat. No. 3,360,046 given to Johnson et al. discloses acement slurry with insulating properties for use in wells. The '046reference teaches the use of 25% to 40% silica flour, and from 10% to50% of vermiculite or perlite. Also, the '046 reference mentions that agelling agent, such as bentonite can be present in the cementcomposition. Also, a dispersing agent can be used in the cement slurry.

[0007] U.S. Pat. No. 4,780,220 given to Peterson discloses a method ofpreparing a drilling and completion fluid. Peterson '220 teaches adrilling mud comprising water, a gelling agent, a defoamer, and at least6% by volume of a glycerine. Glycol is used as the defoamer and watercomprises at least 22%-28% of the composition.

[0008] U.S. Pat. No. 6,103,671 given to Dobson relates to water-basedwell working fluids in drilling, completing, or workover of oil and gaswells. The '671 fluid comprises an amorphous silica viscosifier and awater soluble polyethylene glycol shale inhibitor, the silicaviscosifier added in an amount to increase the thermal stability of thefluid.

[0009] An oil-free water-soluble hydroxyethyl cellulose liquid polymerdispersion is disclosed by Hoff in U.S. Pat. No. 5,985,801. The '801polymer dispersion is used for thickening aqueous mediums of completionand workover fluids. The dispersion comprises hydroxyethyl cellulose andpropylene glycol derivatives including propylene glycol polyetherpolyols and aliphatic propylene glycol ether. The hydroxyethyl celluloseis dispersed rather than dissolved in the propylene glycol derivatives.

[0010] The compositions of both U.S. Pat. No. 5,876,619 given to Skaggset al. and U.S. Pat. No. 5,290,768 given to Ramsay et al. are directedtowards insulating fluids. Ramsay discloses a thixotropic compositioncontaining ethylene glycol and glycol-compatible welan gum. Ramseynarrowly claims a composition consisting of ethylene glycol, a chelatingagent and glycol compatible welan gum in a 0.25% mixture with ethyleneglycol. Skaggs is specifically directed towards scleroglucan as aviscosifier in a polyol base of glycerin or ethylene glycol wherein thescleroglucan is 1% to 3% by weight of the composition and thecomposition contains less than 10% water, preferably 1% to 5% by weightof the composition. Skaggs suggests various uses for the composition inaddition to thermal insulation, including de-icing, ballasting, as apacker material and reservoir work over completion “kill” material.

[0011] Several problems are associated with prior insulatingcompositions, a primary concern being that they can react with thechemicals that are being stored or piped. In the case of a leak, thecomposition could chemically react with the contents to form a hazardoussituation. Compositions in a solid state tend to be porous and wouldallow the travel of leaked chemicals. Gels have been used to restrictthe movement of leaking chemicals.

[0012] Insulating compositions can decompose over time. Some fluids willseparate over time or chemically degrade. A composition with aninsulating component needs to withstand the effects of time to maintainits ability to insulate. A thermally insulating fluid is needed thatprovides insulation to fluids in vessels and pipes without breaking downor reacting with the stored fluids if leakage occurs.

SUMMARY OF THE INVENTION

[0013] The thermally insulating fluid of this invention has relativelylow thermal conductivity as compared to previously known insulatingfluids and is stable over periods of time so as to resist phaseseparation or decomposition. Advantageously, the thermally insulatingfluid has the rheological properties required to support the insulatingfluid components and yet is pumpable so that it can be removed from theinsulating container or piping if necessary. One preferred thermallyinsulating fluid composition comprises a glycol solvent, preferably apropylene glycol solvent, a viscosifier, and optionally, an aqueousbrine or other weighting agent. Under high temperature conditions, suchas deep downhole drilling, a butylene glycol can be used as theinsulating agent in combination with an aqueous brine, and, depending ontemperature, the composition comprises butylene glycol as the solventfor a viscosifier and an aqueous brine.

[0014] The thermal insulating fluid composition of the present inventionadvantageously has lower thermal conductivity thereby increasing itsinsulating properties. Glycol, preferably, propylene glycol isadvantageously used as the insulating agent and solvent for aviscosifier in the present composition because it has been found thatthe propylene glycol in combination with one or more viscosifiers havethe desired lower conductive properties to produce better insulators.One preferred composition can comprise a glycol solvent, preferably aglycol solvent with selected viscosifiers, for example, hydroxy propylmethyl cellulose, hydroxy propyl guar, xanthan, and combinationsthereof, either with or without an aqueous brine solution.

[0015] Weighting agents can be used to yield a variety of densities tomeet hydraulic and thermal requirements. One novel aspect of the presentinvention is the combination of a glycol, preferably propylene glycol,as a solvent for one or more of the selected viscosifiers with aweighting agent selected from a group consisting of soluble organicsalts, soluble inorganic salts, particulate minerals and combinationsthereof.

[0016] In another aspect, the present invention comprises a thermalinsulating fluid of propylene glycol solvent with one or moreviscosifiers measuring about 0.1% by weight to about 10% by weight. Thepropylene glycol solvent measures about 20% to 99.9% by weight with oneor more viscosifiers selected from xanthan, hydroxy propyl methylcellulose, hydroxy propyl guar and combinations thereof. Optionally,aqueous brine concentrations measuring 0.1% to 79.9% may be added. Thesalt of the aqueous brine is selected from NaCl, NaBr, KCl, KBr, CaCl₂,CaBr₂, ZnCl₂, ZnBr₂, NaNO₃, KNO₃, Ca(NO₃)₂, Zn(NO₃)₂ and combinationsthereof.

[0017] In another embodiment, especially useful in high temperatureenvironments, the thermal insulating fluid of the present inventioncomprises butylene glycol and an aqueous brine. Preferably, under hightemperature conditions, one or more viscosifiers can be added to themixture of butylene glycol and brine, wherein the butylene glycol willact as the solvent for the viscosifiers. Alternatively, the glycolsolvent can comprise a combination of propylene glycol and butyleneglycol. Depending on temperature conditions one or more viscosifiers canbe added. The concentrations of the glycol solvents, viscosifiers andaqueous brine, if added, remain equivalent to the propylene glycolthermally insulating fluid described above.

[0018] In a further aspect, the present invention provides a method forproducing a thermal insulating fluid by adding a first viscosifier to anaqueous brine. The viscosifier can be selected from hydroxy propylmethyl cellulose, xanthan and hydroxy propyl guar and combinationthereof. Water is then added followed by a dry salt or concentratedbrine to increase the density. In a separate vessel, a secondviscosifier is added to a glycol solvent. The final step combines thecontents of both vessels to form the more stable thermal insulatingfluid of this invention.

[0019] Another preferred method for producing a thermal insulating fluidutilizing two viscosifiers comprises the steps of: (a) adding a firstviscosifier to an aqueous brine;(b) adding water to the mixture of step(a); (c) adding a dry salt or concentrated brine to increase density;(d) in a separate vessel, adding a second viscosifier to propyleneglycol; (e) combining the mixture of step (c) to the mixture of step(d).

[0020] In this preferred method for producing a thermal insulatingfluid, the first and second viscosifiers are selected from hydroxypropyl methyl cellulose, xanthan and hydroxy propyl guar andcombinations thereof

[0021] Thermally insulating fluid can be used with multi-walled vesselssuch as thermal units, tanks, or concentric piping wherein two walls ofthe unit form a sealable cavity for receiving the insulating fluid.Concentric piping for transporting fluids subject to varying temperatureconditions require removable insulating fluids to maintain thetemperature of the fluids being piped, pumping hydrocarbons for on/offshore oil and gas fields, for example. Double-walled tanks that are usedto store chemicals which must be maintained at a specific temperaturealso benefit from this insulating composition. One example of such a useis the storage of highly volatile liquids, namely gasoline or aqueousammonia. This invention is also applicable to other thermal units,including coolers and refrigeration units, that have the common problemof undesirable heat transfer. One preferred method of applying theinsulating fluid composition of this invention is to inject thethermally insulating fluid into the cavity formed by the walls of thevessel or piping and then seal off the opening. If the insulating fluidneeds to be removed, the opening can be unsealed and the insulatingfluid pumped out in ways commonly known in the art.

[0022] The thermally insulating fluids may either be used alone or incombination with other insulating materials such as vacuum insulatedtubing; insulation coated tubing and particulate insulating materials,namely plastics, glass beads, foams and hollow spheres.

DETAILED DESCRIPTION OF THE INVENTION

[0023] The present invention relates to an innovative thermal insulatingfluid, a method of producing the thermal insulating fluid and methods ofinsulating that are used to reduce heat transfer. The insulating fluidand method of application of the composition of this invention isespecially effective when used with multi-walled containers by insertionof the fluid into a sealable cavity defined by the walls. The low heatconduction properties of the present thermal insulating fluid allows itto be applicable in either extremes of temperature, high heat found indeep well drilling or piping in the frozen tundra for example.

[0024] In one preferred embodiment, the composition of the presentthermal insulating fluid comprises a glycol solvent for viscosifiers,one or more viscosifiers, and, optionally an aqueous brine. Glycolsexhibit good insulating properties when, according to the composition ofthis invention, they are used as a solvent for a viscosifier. In onepreferred composition, the glycol is a propylene glycol that can beselected from mono-propylene glycol, di-propylene glycol, tri-propyleneglycol, tetra-propylene glycol or combinations thereof. The one or moreviscosifiers can be selected from hydroxy propyl methyl cellulosecommercially available as Methocell OS from the Dow Chemical Co.,xanthan commercially available as Rhodopol 23 from Rhodia, hydroxypropyl guar commercially available as Jaguar 413 from Rhodia, andcombinations thereof.

[0025] When thermal insulation is required under high temperatureconditions, the glycol can be butylene glycol and one preferred thermalinsulating fluid comprises butylene glycol in an aqueous brine. Becausebutylene glycol is viscous at lower temperatures, additionalviscosifiers are not necessary until the butylene glycol thermalinsulating fluid is considered for use under higher temperaturesconditions, above 190° F., for example. Butylene glycol can be selectedfrom 1,2 butylene glycol, 2,3 butylene glycol, 1,3 butylene glycol, 1,4butylene glycol, or combinations thereof.

[0026] One preferred embodiment of the thermal insulating fluidcomprises a propylene glycol solvent for a viscosifier and aviscosifier. The glycol is the solvent and water content of the fluidcan range from about 0.1% to about 5.0%. Alternatively, an aqueous brinemay be added as a weighting agent. In one aspect, the preferred thermalinsulating fluid comprises a propylene glycol used as a solvent forviscosifiers in an amount comprising about 20% to 99.9% by weight, andone or more viscosifiers in an amount comprising about 0.1% by weight toabout 10% by weight. In this composition, the one or more viscosifierscan be selected from xanthan, hydroxy propyl methyl cellulose, hydroxypropyl guar or combinations thereof. An alternative compositionutilizing an aqueous brine can comprise a propylene glycol solvent forviscosifiers in an amount comprising about 20% to 99.8% by weight, oneor more viscosifiers in an amount comprising about 0.1% by weight toabout 10% by weight, the one or more viscosifiers selected from xanthan,hydroxy propyl methyl cellulose, hydroxy propyl guar and combinationsthereof; and 0.1% to 79.9% aqueous brine.

[0027] Another preferred thermal insulating fluid comprises a propyleneglycol solvent for viscosifiers, viscosifiers in an amount comprisingabout 0.1% by weight to about 10% by weight, the propylene glycol in anamount comprising about 20% to 99.8% by weight, the viscosifierscomprising xanthan and hydroxy propyl guar and 0.1% to 79.9% aqueousbrine.

[0028] Under high temperature industrial processes such as deep welldrilling, the present invention utilizes a thermal insulating fluidcomprising a butylene glycol and an aqueous brine. Alternatively, thethermal insulating fluid comprises a butylene glycol solvent forviscosifiers and one or more viscosifiers. The addition of an aqueousbrine is optional. In still another alternative composition, usefulunder higher geothermal conditions, the thermal insulating fluid is acombination of a propylene glycol solvent and a butylene glycol solventfor viscosifiers, the viscosifiers in an amount comprising about 0.1% byweight to about 10% by weight, the combination of propylene glycol andbutylene glycol in an amount comprising about 20% to 99.8% by weight,the viscosifiers selected from xanthan, hydroxy propyl methyl cellulose,hydroxy propyl guar and combinations thereof. An addition of 0.1% to79.9% aqueous brine is optional. In one aspect, the viscosifierscomprise xanthan and hydroxy propyl guar.

[0029] The weighting agents used in the practice of this invention canbe selected from a group consisting of soluble inorganic salts, solubleorganic salts, particulate minerals and combinations thereof. In oneembodiment, the one or more soluble inorganic salts are selected fromNaCl, NaBr, KCl, KBr, CaCl₂, CaBr₂, ZnCl₂, ZnBr₂, NaNO₃, KNO₃, Ca(NO₃)₂,Zn(NO₃)₂ and combinations thereof. Alternatively, the weighting agentcan be one or more soluble organic salts selected from sodium formate,potassium formate, and/or cesium formate and combinations thereof. Theorganic salt weighting agent can also be selected from sodium acetate,potassium acetate, and combinations thereof. Alternatively, weightingagents can also be selected from one or more particulate minerals suchas hematite, magnetite, illmenite, barite, siderite, celestite,dolomite, calcite, scheelite, apatite and combinations thereof.

[0030] Plastics, microspheres, glass beads and combinations thereof canalso be used as additional insulating materials or weighting agents. Inone preferred embodiment, the insulating particulates comprisemicrospheres such as glass microspheres, either solid glass or hollow.If hollow, the glass preferably comprises sufficient compressivestrength to withstand a pressure range from about 10 psi to about 10,000psi. The compression strength of the glass shell is selected accordingto the environment of the application of insulating fluid. In onepreferred embodiment, the insulating particulates comprise a combinationof insulating hollow glass microspheres and insulating solidparticulates, for example, insulating hollow glass microspheres andsolid glass microspheres.

[0031] Alternatively the insulating particulates can comprise plasticmicrospheres, also having compressive strength to withstand downholepressures. The hollow insulating particulates, glass or plastic, canencapsulate a fluid. The cavity of the hollow spheres, can be filed witha gas or liquid. Preferably the particulates encapsulate air, air beingone of the better insulators. Additional insulating materials comprisevacuum insulated tubing, insulation-coated tubing, foams, and phasechange materials in the form of coatings or particles.

[0032] In another aspect of this invention, one preferred thermalinsulating fluid comprises a propylene glycol solvent for a viscosifierand hydroxy propyl methyl cellulose. The addition of an aqueous brine isoptional. Another preferred thermal insulating fluid comprises apropylene glycol solvent for a viscosifier and a combination of xanthanand hydroxy propyl guar, optionally an aqueous brine can be added to thefluid.

[0033] One preferred method for producing thermal insulating fluid ofthis invention comprises the following:

[0034] (a) adding a viscosifier to an aqueous brine;

[0035] (b) adding water to the mixture of step (a);

[0036] (c) adding a dry salt or concentrated brine to increase density;

[0037] (d) adding propylene glycol to the mixture of step (c).

[0038] An alternative method utilizing two viscosifiers comprises thesteps of:

[0039] (a) adding a first viscosifier to an aqueous brine;

[0040] (b) adding water to the mixture of step (a);

[0041] (c) adding a dry salt or concentrated brine to increase density;

[0042] (d) in a separate vessel, adding a second viscosifier topropylene glycol;

[0043] (e) combining the mixture of step (c) to the mixture of step (d).

[0044] In this method for producing a thermal insulating fluid the firstand second viscosifiers are selected from hydroxy propyl methylcellulose, xanthan and hydroxy propyl guar and combinations thereof.

[0045] One preferred method for producing a thermal insulating fluidhaving xanthan and guar as viscosifiers comprises:

[0046] (a) adding xanthan to an aqueous brine;

[0047] (b) adding water to the mixture of step (a);

[0048] (c) adding a dry salt or concentrated brine to increase density;

[0049] (d) in a separate vessel, adding hydroxyl propyl guar topropylene glycol;

[0050] (e) combining the mixture of step (c) to the mixture of step (d).

[0051] The aqueous brine can be selected from NaCl, NaBr, KCl, KBr,CaCl₂, CaBr₂, ZnCl₂, ZnBr₂, NaNO₃, KNO₃, Ca(NO₃)₂, Zn(NO₃)₂ andcombinations thereof. Any of the above methods can further comprise theaddition of a second viscosifier, hydroxyl propyl guar for example, to acombination of propylene glycol and butylene glycol in step (d).

[0052] The usefulness of the thermally insulating fluid described hereinis multifold. Concentric piping for transporting fluids subject tovarying temperature conditions often require removable insulating fluidsto maintain the temperature of the fluids being piped, pumpinghydrocarbons on shore or offshore, for example. Double-walled tanks thatare used to store chemicals which must be maintained at a specifictemperature also benefit from this insulating composition. One exampleof such a use is the storage of highly volatile liquids such as gasolineor aqueous ammonia. This invention is also applicable to other thermalunits, including coolers and refrigeration units that have the commonproblem of undesirable heat transfer.

[0053] One effective use of the thermally insulating fluid is in oilfield production to protect the loss of heat in subterranean piping thatis subject to cold weather conditions, deep sea wells, Arctic drilling,Alaska and similar environments. Many such wells have several concentriclayers of piping so that the double-wall cavity is available forreceiving the injected insulating fluid. Protecting the permanentlyfrozen ground, such as permafrost from the heat of pipes transportingpetrochemicals is another consideration. The injection of the thermallyinsulating fluid of this invention between double-walled piping canreduce damage to the permafrost.

[0054] For the purpose of illustration, reference hereafter is made, forconvenience and not to limit the scope of this composition or itsmethods. The detailed description will describe the composition and useof insulating fluid in downhole pipe used in oil field production. Theretention of high temperatures within the tubing is necessary to inhibitthe accumulation of asphaltene, paraffin and scale inside pipes. Thepresence of hydrates or paraffins in pipe will slow down products fromtraveling through the pipe and reduce or halt production. Downholepiping typically comprises casing, tubing for drilling fluids and theproduction of the hydrocarbons and several intermediate layers of pipe.The thermally insulating fluid of this invention is injected in theannulus or cavity created by two adjacent walls of piping therebyprotecting the high temperatures of the production fluids from the coldtemperatures of the subterranean environment.

[0055] One method of insulating multi-walled systems comprises injectinga thermally insulating fluid having a composition as described above inbetween two adjacent walls of a multi-walled or concentric walledsystem. The concentric walls of the system form an annulus or cavity.The insulating fluid of this invention can be injected into this cavityand then the cavity is sealed. Advantageously, removal of the insulatingfluid can be accomplished by standard, known pumping methods because ofthe fluid nature of the insulation of this invention.

[0056] One method of insulating multi-walled pipes comprises injecting athermally insulating fluid comprising one of the above-describedcompositions into the annulus or cavity defined by two of the walls ofthe multi-walled or concentric piping. This method is adapted toinsulate subterranean pipes in low temperature conditions, deep-sea bedpiping for example. The thermally insulating fluid can comprise aninsulating microspheres or foam, such as aphrons. A method forprotecting permafrost can comprise insulating double-walled pipes laidwithin the permafrost by injecting the annulus between the adjacentwalls with a thermally insulating fluid having one of theabove-described compositions. The cavity can be sealed.

[0057] Similarly, a method of insulating double-walled tanks comprisesinjecting the thermally insulating fluid of the present invention intothe annulus defined by the adjacent walls of the tanks. The annulus canbe sealed and then reopened if the insulating fluid needs to be removed.Removal is by commonly known methods of pumping fluids. Double-walledinsulating vessels such as thermal packs or coolers can be insulated byinserting the thermally insulating fluid of this invention between theadjacent walls of the vessels. A method of insulating double-walledrefrigeration units comprises inserting the thermally insulating fluidhaving the composition described above between the adjacent walls of therefrigeration units. A specialized use for the thermally insulatingfluid of this invention is with protecting subsea wellheads subjected totemperature extremes. The method of insulating a subsea well head andits control equipment comprises surrounding the subsea well head and itscontrol equipment with a container, a flexible sac for example, thatencloses a thermal insulating fluid having a composition selected from agroup consisting of compositions as described above.

EXAMPLES

[0058] The thermal conductivity of propylene glycols of this inventionis significantly lower than the thermal conductivity of glycerin orethylene glycol of the prior art as illustrated by the following table:

[0059] Thermal Conductivity Comparison Data Comparison of Polyol ThermalConductivities % Difference Vs Material btu/hr-ft-° F. Tri-PropyleneGlycol Glycerin 0.164 80 Ethylene Glycol 0.153 68 Mono-Propylene Glycol0.119 31 Di-Propylene Glycol 0.095 4 Tri-Propylene Glycol 0.091 0

[0060] The thermal conductivity data for the glycerin, ethylene glycoland mono-propylene glycol are from Perry's Chemical Engineer' Handbook,6 ed., 1984. The data for the remaining materials are from manufacture'sliterature.

Example 1

[0061] It has been determined that scleroglucan is not an effectiveviscosifier for propylene glycols. U.S. Pat. No. 5,876,619 teaches theviscosification of glycerin or ethylene glycol by the addition of 1% to3% scleroglucan and heating the mixture to 195° F. for two hours, thencooling. In an effort to apply U.S. Pat. No. 5,876,619 to theviscosification of propylene glycol, 4 grams of scleroglucan (Biovis bySKW) was added to 356 grams of propylene glycol (Drillcol 7234 byShrieve Chemical). This resulted in a 1.1 weight % mixture. The mixturewas heated to 195° F., held for two hours, and then cooled to roomtemperature. The mixture of scleroglucan and propylene glycol did notviscosity and the scleroglucan settled out of the mixture as a solid onstanding. From this experiment it is concluded that scleroglucan is notsoluble in propylene glycol.

Example 2

[0062] Thermal Conductivity Heat Capacity Test Results

[0063] Below is the composition of three samples used for testing.Sample A Sample B Sample C Density  8.5  8.67  9.5 ppg (pounds pergallon) Wt. %  0%  5%  26% 14.2 ppg propylene 356 345.5 293.9 glycol14.2 ppg  0  18.3 104.5 CaBr2 hydroxy  4  2  2 propol methyl cellulosebiocide  0  0.1  0 oxygen  0  0.05  0 scavanger corrosion  0  0.05  0inhibitor

[0064] Sample A is manufactured by making viscosified propylene glycol.The viscosified propylene glycol is heated to between 180° F. and 200°F. and mixed for about 2 hours.

[0065] Samples B and C are manufactured by separately making viscosifiedbrine and viscosified propylene glycol. Viscosified brine is added tothe viscosified propylene glycol and mixed for 1 hour.

[0066] The thermal properties of the three sample formulationscontaining propylene glycol and 14.2 ppg brine have been measured by anoutside laboratories, Anter Laboratories, 3M Laboratories and SRI.

[0067] Multiphase Systems, Inc. (MSi) has computer estimated the cooldown times for a dual production riser system using the propyleneglycol+14.2 ppg brine gels as follows: TABLE 1 Thermal Properties andMSi Cool Down Times weight Cp K Cool % % Density (Btu/ (Btu/ DownImprove- Sample ID brine (ppg) lb-° F.) hr-ft-° F.) (hrs) ment [Commer-9.5 0.510 0.280 3.3 Basis cially available product]] Sample A  0% 8.50.590 0.0924 7.8 136% Sample B  5% 8.67 0.553 0.0953 7.6 130% Sample C26% 9.5 0.471 0.1063 6.6 100%

Example 3

[0068] Description of Typical Composition and Manufacturing ProcessMethod of producing Viscosified Propylene Glycol Lab step DescriptionBarrel* 1 Add 14.2 ppg CaBr2 brine to vessel.  393.8 g 2 Slowly addxanthan biopolymer powder.  5.00 g 3 Mix 15 minutes to homogenize. 4 Addwater to make 12.5 ppg brine.  94.20 g 5 Mix 40 minutes. Batch willbecome very viscous. 6 Slowly add dry CaBr2 to make 14.2 ppg. 108.00 g 7Continue mixing while preparing  339.3 g viscosified propylene glycol. 8In a separate vessel add propylene glycol.  339.3 g 9 Add guar gum topropylene glycol.   8.0 g 10 Mix 2 hours. 11 Allow mixing to increasetemperature  339.3 g to at least 90 F. 12 Slowly inject viscosifiedbrine from  38.3 g Step 6 into viscosified propylene glycol from Step 9with vigorous mixing with a Hamilton Beach mixer. 13 Mix 1 hour 14 AddBiocide  0.05 g 15 Add a corrosion inhibitor**  0.05 g 16 Add an oxygenscavenger***   0.1 g 17 Continue mixing 30 minutes until mixture ishomogeneous. 18 Sample and measure Fann 35 viscosity.

1. A thermal insulating fluid comprising: a glycol solvent forviscosifiers; one or more viscosifiers, and an aqueous brine.
 2. Athermal insulating fluid comprising: a glycol solvent for viscosifiers;one or more viscosifiers, the viscosifiers selected from hydroxy propylmethyl cellulose, xanthan and hydroxy propyl guar and combinationsthereof; and an aqueous brine.
 3. A thermal insulating fluid comprising:a propylene glycol solvent for a viscosifier; and a viscosifier.
 4. Athermal insulating fluid comprising: a propylene glycol solvent for aviscosifier; a viscosifier; and an aqueous brine.
 5. A thermalinsulating fluid comprising: a propylene glycol solvent for aviscosifier; a viscosifier selected from a group consisting of hydroxypropyl methyl cellulose, hydroxy propyl guar, xanthan or combinationsthereof.
 6. The thermal insulating fluid of claim 5 wherein thepropylene glycol solvent the propylene glycol is selected from a groupconsisting of mono-propylene glycol, di-propylene glycol, tri-propyleneglycol, tetra-propylene glycol and combinations thereof.
 7. The thermalinsulating fluid of claim 5 further comprising additional insulatingmaterials.
 8. The thermal insulating fluid of claim 7 wherein theadditional insulating materials are selected from plastics,microspheres, both hollow and solid, glass beads, vacuum insulatedtubing, insulation-coated tubing, foams, phase change materials, andcombinations thereof.
 9. The thermal insulating fluid of claim 5 furthercomprising an aqueous brine
 10. A thermal insulating fluid comprising: apropylene glycol solvent for a viscosifier; a viscosifier selected froma group consisting of hydroxy propyl methyl cellulose, hydroxy propylguar, xanthan and combinations thereof; and one or more weightingagents.
 11. The thermal insulating fluid of claim 10 wherein theweighting agents are selected from a group consisting of solubleinorganic salts, soluble organic salts, particulate minerals andcombinations thereof.
 12. The thermal insulating fluid of claim 11wherein the one or more soluble inorganic salts are selected from NaCl,NaBr, KCl, KBr, CaCl₂, CaBr₂, ZnCl₂, ZnBr₂, NaNO₃, KNO₃, Ca(NO₃)₂,Zn(NO₃)₂ and combinations thereof.
 13. The thermally insulating fluid ofclaim 11 wherein the one or more soluble organic salts are selected fromsodium formate, potassium formate, cesium formate, sodium acetate,potassium acetate, cesium acetate, and combinations thereof.
 14. Thethermally insulating fluid of claim 11 wherein the one or moreparticulate minerals are selected from hematite, magnetite, illmenite,barite, siderite, celestite, dolomite, calcite, scheelite, apatite andcombinations thereof.
 15. The thermally insulating fluid of claim 10wherein the one or more weighting agents comprise plastics,microspheres, glass beads and combinations thereof.
 16. A thermalinsulating fluid comprising: a propylene glycol solvent for aviscosifier; and a viscosifier comprising hydroxy propyl methylcellulose.
 17. The thermally insulating fluid of claim 16 furthercomprising an aqueous brine.
 18. A thermal insulating fluid comprising:a propylene glycol solvent for viscosifiers; and viscosifiers comprisingxanthan and hydroxy propyl guar.
 19. A thermal insulating fluidcomprising: a propylene glycol solvent for viscosifiers; viscosifierscomprising xanthan and hydroxy propyl guar; and an aqueous brine.
 20. Athermal insulating fluid comprising: a propylene glycol solvent forviscosifiers, one or more viscosifiers in an amount comprising about0.1% by weight to about 10% by weight, the propylene glycol in an amountcomprising about 20% to 99.9% by weight, the one or more viscosifiersselected from xanthan, hydroxy propyl methyl cellulose, hydroxy propylguar and combinations thereof.
 21. A thermal insulating fluidcomprising: a propylene glycol solvent for viscosifiers, one or moreviscosifiers in an amount comprising about 0.1% by weight to about 10%by weight, the propylene glycol in an amount comprising about 20% to99.8% by weight, the one or more viscosifiers selected from xanthan,hydroxy propyl methyl cellulose, hydroxy propyl guar and combinationsthereof; and 0.1% to 79.9% aqueous brine.
 22. A thermal insulating fluidcomprising: a propylene glycol solvent for viscosifiers, viscosifiers inan amount comprising about 0.1% by weight to about 10% by weight, thepropylene glycol in an amount comprising about 20% to 99.8% by weight,the viscosifiers comprising xanthan and hydroxy propyl guar.
 23. Athermal insulating fluid comprising: a propylene glycol solvent forviscosifiers, viscosifiers in an amount comprising about 0.1% by weightto about 10% by weight, the propylene glycol in an amount comprisingabout 20% to 99.8% by weight, the viscosifiers comprising xanthan andhydroxy propyl guar 0.1% to 79.9% aqueous brine.
 24. A thermalinsulating fluid comprising: a butylene glycol and an aqueous brinewithin a range of about 0.1% to about 79.9%.
 25. A thermal insulatingfluid comprising: a butylene glycol solvent for viscosifiers; and one ormore viscosifiers.
 26. A thermal insulating fluid comprising: a butyleneglycol solvent for viscosifiers; one or more viscosifiers, and anaqueous brine.
 27. A thermal insulating fluid comprising: a combinationof a propylene glycol solvent and a butylene glycol solvent forviscosifiers, the viscosifiers in an amount comprising about 0.1% byweight to about 10% by weight, the combination of propylene glycol andbutylene glycol in an amount comprising about 20% to 99.8% by weight,the viscosifiers selected from xanthan, hydroxy propyl methyl cellulose,hydroxy propyl guar and combinations thereof.
 28. The thermallyinsulating fluid of claim 27 further comprising 0.1% to 79.9% aqueousbrine.
 29. A thermal insulating fluid comprising: a combination ofpropylene glycol solvent and a butylene glycol solvent for viscosifiers,the combination of propylene glycol and butylene glycol in an amountcomprising about 20% to 99.8% by weight, one or more viscosifiers in anamount comprising about 0.1% by weight to about 10% by weight, theviscosifiers comprising xanthan and hydroxy propyl guar.
 30. A thermalinsulating fluid comprising a combination of a propylene glycol solventand a butylene glycol solvent for viscosifiers, the combination ofpropylene glycol and butylene glycol in an amount comprising about 20%to 99.8% by weight, one or more viscosifiers in an amount comprisingabout 0.1% by weight to about 10% by weight, the viscosifiers comprisingxanthan and hydroxy propyl guar; and 0.1% to 79.9% aqueous brine.
 31. Amethod for producing a thermal insulating fluid comprising: a) adding aviscosifier to an aqueous brine; b) adding water to the mixture of step(a); c) adding a dry salt to increase density; d) adding propyleneglycol to the mixture of step (c).
 32. A method for producing a thermalinsulating fluid comprising: (a) adding a first viscosifier to anaqueous brine; (b) adding water to the mixture of step (a); (c) adding adry salt to increase density; (d) in a separate vessel, adding a secondviscosifier to propylene glycol; (e) combining the mixture of step (c)to the mixture of step (d).
 33. A method for producing a thermalinsulating fluid comprising: (a) adding a first viscosifier to anaqueous brine, the viscosifier selected from hydroxy propyl methylcellulose, xanthan and hydroxy propyl guar and combinations thereof; (b)adding water to the mixture of step (a); (c) adding a dry salt toincrease density; (d) in a separate vessel, adding a second viscosifierto propylene glycol, the viscosifier selected from hydroxy propyl methylcellulose, xanthan and hydroxy propyl guar and combinations thereof; (e)combining the mixture of step (c) to the mixture of step (d).
 34. Amethod for producing a thermal insulating fluid comprising: (a) addingxanthan to an aqueous brine; (b) adding water to the mixture of step(a); (c) adding a dry salt to increase density; (d) in a separatevessel, adding hydroxyl propyl guar to propylene glycol; (e) combiningthe mixture of step (c) to the mixture of step (d).
 35. A method forproducing a thermal insulating fluid comprising: e) adding a viscosifierto an aqueous brine; f) adding water to the mixture of step (a); g)adding a concentrated brine to increase density; h) adding propyleneglycol to the mixture of step (c).
 36. A method for producing a thermalinsulating fluid comprising: (a) adding a first viscosifier to anaqueous brine; (b) adding water to the mixture of step (a); (c) adding aconcentrated brine to increase density; (d) in a separate vessel, addinga second viscosifier to propylene glycol; (e) combining the mixture ofstep (c) to the mixture of step (d).
 37. A method for producing athermal insulating fluid comprising: (a) adding a first viscosifier toan aqueous brine, the viscosifier selected from hydroxy propyl methylcellulose, xanthan and hydroxy propyl guar and combinations thereof; (b)adding water to the mixture of step (a); (c) adding a concentrated brineto increase density; (d) in a separate vessel, adding a secondviscosifier to propylene glycol, the viscosifier selected from hydroxypropyl methyl cellulose, xanthan and hydroxy propyl guar andcombinations thereof; (e) combining the mixture of step (c) to themixture of step (d).
 38. A method for producing a thermal insulatingfluid comprising: (a) adding xanthan to an aqueous brine; (b) addingwater to the mixture of step (a); (c) adding a concentrated brine toincrease density; (d) in a separate vessel, adding hydroxyl propyl guarto propylene glycol; (e) combining the mixture of step (c) to themixture of step (d).
 39. The method of claim 38 wherein the aqueousbrine is selected from NaCl, NaBr, KCl, KBr, CaCl₂, CaBr₂, ZnCl₂, ZnBr₂,NaNO₃, KNO₃, Ca(NO₃)₂, Zn(NO₃)₂, and combinations thereof.
 40. Themethod of claim 38 further comprising adding hydroxyl propyl guar to acombination of propylene glycol and butylene glycol in step (d).
 41. Amethod of insulating a multi-walled system comprising: injecting athermally insulating fluid having a composition selected from a groupconsisting of compositions defined in any of claims 1-30 into the one ormore cavities defined by the walls of the multi-walled system.
 42. Amethod of insulating multi-walled pipes comprising: injecting athermally insulating fluid having a composition selected from a groupconsisting of compositions defined in any of claims 1-30 into one ormore cavities defined by the walls of the pipe.
 43. The method of claim42 wherein the multi-walled pipes are subterranean pipes.
 44. The methodof claim 42 wherein the multi-walled pipes are sea bed pipes.
 45. Amethod of protecting permanently frozen ground comprising: insulatingdouble-walled pipes by injecting into the annulus defined by the walls,a thermally insulating fluid having a composition selected from thegroup consisting of compositions defined in any of claims 1-30.
 46. Amethod of insulating a double-walled tank comprising: inserting athermally insulating fluid having a composition selected from a groupconsisting of compositions defined in any of claims 1-30 into an cavitydefined by walls of the tank.
 47. A method of insulating a double-walledvessel comprising: inserting a thermally insulating fluid having acomposition selected from a group consisting of compositions defined inany of claims 1-30 between the adjacent walls of the vessel.
 48. Amethod of insulating a double-walled thermal unit comprising: insertinga thermally insulating fluid having a composition selected from a groupconsisting of compositions defined in any of claims 1-30 between theadjacent walls of the thermal unit.
 49. A method of insulating adouble-walled refrigeration unit comprising: inserting a thermallyinsulating fluid having a composition selected from a group consistingof compositions defined in any of claims 1-30 between the adjacent wallsof the refrigeration unit.
 50. A method of insulating a multi-walledsystem comprising: injecting a thermally insulating fluid comprisingbutylene glycol into the one or more cavities defined by the walls ofthe multi-walled system.
 51. A method of insulating a double-walledheating unit comprising: inserting a thermally insulating fluid having acomposition selected from a group consisting of compositions defined inany of claims 1-30 into an cavity.
 52. A method of insulating a subseawell head and its control equipment comprising: surrounding the subseawell head and its control equipment with a container containing athermal insulating fluid having a composition selected from a groupconsisting of compositions defined in any of claims 1-30.